DAMASCUS — The Arab League on Sunday called on Syrian President Bashar al-Assad to hand over power to his vice president under the terms of a transition plan similar to that which paved the way for the departure, hours earlier, of Yemen’s president for the United States.

The announcement of the plan at a meeting of Arab foreign ministers in Cairo signaled growing Arab frustration with Assad’s failure to implement the terms of a peace plan to which he agreed in November, and it offered the clearest indication yet that Arab states want him to step down.

The plan laid down a timetable under which negotiations with the opposition would begin in two weeks and a national unity government would be formed within two months. Assad would then leave office ahead of elections to be held within three months. It was not immediately clear which of two Syrian vice presidents, Farouk al-Shara or Najah al-Attar, would be expected to take over.

The Syrian National Council, the main Syrian opposition coalition, welcomed the initiative as a step toward Assad’s departure, the group’s leader, Burhan Ghalioun, told reporters in Cairo. Activists in Syria have repeatedly said, however, that they will not negotiate with Assad.

There was no immediate response from the Syrian government, and a spokesman did not respond to calls seeking comment.

But Assad vowed in a defiant speech this month that he would not step down unless the Syrian people asked him to, and the Arab League’s secretary general, Nabil Elaraby told reporters that the bloodshed would have to stop before the negotiations could start, a condition that cast into doubt the likelihood the plan would succeed at a time of rapidly escalating violence.

“The chances of that happening are next to zero, and I also can’t imagine Assad will accept this,” said Salman Shaikh, director of the Brookings Doha Center in Qatar. “At best, this is throwing down something that is certainly new but has little chance of success.”

The league said it would refer the plan for endorsement to the U.N. Security Council, indicating that Arab states are prepared to seek wider international involvement in the Syria crisis.

Monitoring expanded

Qatari Prime Minister Hamad Bin Jasim al-Thani told reporters in Cairo that the plan is much like the one brokered by the Gulf Cooperation Council under which Yemeni President Ali Abdullah Saleh agreed to transfer power to his vice president. Saleh left Yemen on Sunday and is expected to travel to the United States for medical care.

The Syria plan appeared to have overwhelming Arab endorsement. Only Lebanon, whose government is closely aligned with Syria’s, objected. Algeria expressed “reservations.” Iraq, which had previously abstained from sanctioning Syria, seemed to have signed on to the initiative.

But there were no indications as to what steps would be taken if Assad failed to comply. Hours earlier, Saudi Arabia said it was withdrawing its observers from a mission to monitor the violence in Syria, in a hint of underlying divisions within the league over how to proceed should the violence continue to escalate. At the Sunday meeting, league officials agreed to extend the monitoring mission for another month and expand it to include extra observers.

“The goal is to stop the bloodshed,” Hamad said, citing Assad’s failure to comply with league demands to withdraw troops from residential areas, stop killing protesters and release political prisoners. “We do not wish to prolong this.”

22 reported killed Sunday

Activist groups reported that 22 people were killed by security forces Sunday in incidents around the country, nine of them in Douma, a suburb on the northeastern edge of Damascus where fierce clashes have been reported between troops and rebels fighting in the name of the Free Syrian Army.

There were unconfirmed reports that security forces had withdrawn from parts of the town, less than a week after the army was forced to pull out from the town of Zabadani, 20 miles to the west.

In a video posted on YouTube, a masked, uniformed soldier holding a rifle and flanked by other armed men read a statement claiming that the Free Syrian Army had driven the army from Douma. If government forces attempt to retake the town, the man warned, “We will fire rockets at the presidential palace and execute the five senior officers who are our prisoners.”

The official news agency, SANA, on Sunday reported that seven members of the security forces had been killed in attacks, including a brigadier general in charge of “e-warfare” who was assassinated in the town of Rankous, outside Damascus.

Liz Sly is The Washington Post’s Beirut bureau chief, covering Lebanon, Syria and the wider region. She has spent more than 17 years covering the Middle East, including the first and second Iraq wars. Other postings include Washington, Africa, China, Afghanistan and Italy.